Rabu, 26 Januari 2011

Calibers

The caliber of any firearm is the measurement of the bore of its barrel. It could be measured directly as the diameter of the bore, or some intermediate system could be used as in the case of shotguns, where the caliber or gauge equals the number of lead ball bullets of that diameter which could be molded from one pound of lead. In the case of rifled firearms, the caliber is the measured diameter between lands or grooves of the rifling (see the picture). However, for many reasons actual (measured) caliber may differ from the caliber designation. Most often this misnomer is based on historical or marketing issues. Another source of complications is that there are two measuring systems used worldwide – the metric system and the imperial or inch system. Metric calibers are measured in millimeters, i.e. “7.65 mm” or “9 mm”; Inch calibers are measured in hundredths or thousandths of an inch, with the omission of the leading zero, i.e. “.30” or “.300” (0.30 inch or 7.62mm) or “.45” (0.45 inch or 11.43mm). The direct relationship between metric and inch calibers is represented as 1 inch = 25.4 millimeter, or 1 millimeter = 0.039 inch. In some cases, the nominal inch caliber is the same as the bore diameter (between the lands), as in the case of many .30 caliber weapons that have bore diameters of 0.30 inch or 7.62mm. In other cases, the nominal caliber may match the bullet diameter (slightly wider than the bore) e.g. the .40 S&W. However, in a few cases, the nominal inch calibers have no direct relationship with actual bore or bullet diameter, as with .38 caliber rounds which have bullet diameters ranging from 0.357 to 0.401 inches; these cartridges retain their misleading designations from the age of black powder revolvers. Metric caliber designations tend to be more accurate, but may still vary between whether bore (e.g. 7.62mm) or bullet (e.g. 9mm) diameters are used.

Also, even if two firearms have exactly the same actual caliber, they may use cartridges of very different size and power, i.e. Soviet TT pistol and US M1 Garand rifle both have bores of 7.62mm diameter, but their cartridges are very different in size and power. Therefore, in most cases it is insufficient to know just the caliber of a firearm to procure suitable ammunition, and some additional information needs to be provided. The simplest way is to give any cartridge its own name, i.e. 9mm Steyr and 9mm Luger, or .357 Magnum and .357 SIG. In either case, the calibers (bullet diameters) are the same, but the cartridge shapes, dimensions and power are different, and they are NOT interchangeable. However, there are far too many cartridges to give them all names, so the most convenient (and most common) way with metric designations is to use the case length in conjunction with the caliber. The typical designation that follows this pattern is 9x19, where “9” means the caliber and “19” is the cartridge case length, both measured in millimeters. If several cartridges of different properties have same caliber and case length, some additional information must be provided, usually in the form of a name or suffix, which distinguishes the shape of case head. The sample of the “name” use is 9x23 Largo / Bergmann and 9x23 Steyr cartridges, which were independent developments but are virtually indistinguishable in size and power. Another example is 9x23 Winchester, which, while having the same external dimensions as previous two 9x23 cartridges, has thicker case walls and thus can withstand heavier pressures; this cartridge can be easily loaded into firearm designed for either of former cartridges, but to do so would be extremely dangerous! Yet another example is a fourth cartridge with the same caliber and case length, the 9x23SR, more generally known as .38 Super Automatic or simply .38 Super. This cartridge has semi-rimmed case, that is, it has both the extraction groove and a diminutive rim, as it was designed in around 1898 to be used both in semi-automatic pistols and revolvers. Another example of similar designations but different actual dimensions are 9x18 PM and 9x18 Police cartridges. While these are identical in designations, actual calibers are different, as the 9mm PM bullet has an actual diameter of 9.2mm, and the 9mm Ultra has an actual bullet diameter of 9.02mm. Therefore, mismatching one such cartridge for another may be very dangerous for both gun and shooter. The source of this mismatch is that most western calibers are measured between the grooves of the rifling, and therefore are same as actual bullet diameter; in Russia and USSR, some calibers were measured between the lands of the rifling, therefore actual bullet diameter is bigger than measured caliber.Considering all said above, great care must be exerted when selecting proper ammunition for any firearm.

Bullet types

Many and various bullet types have been developed for fighting, training and other applications; only the most common are mentioned below.

Lead bullets are the oldest type and today used mostly in revolver and small-bore rimfire ammunition. These are formed from lead, or more often, an alloy of lead and antimony. Such bullets are inexpensive but usually can’t withstand higher velocities, and produce significant lead fouling in a rifled bore during prolonged use.

LRN - Lead Round-Nose bullet

LHP - Lead HollowPoint bullet

LSWC - Lead Semi-WadCutter bullet

LWC - Lead WadCutter bullet

Jacketed bullets are the most common and are the only available for military weapons due to international treaties. Such bullets are designed using a lead core that is enclosed by a gilding-metal jacket. These bullets are known for good penetration, but stopping power is often less significant than that of expanding bullets. Jacketed bullets are sometimes referred as “ball” bullets on historical grounds.

FMJ - Full Metal Jacket bullet (also known as 'ball' bullet)

Expanding bullets include Hollow-point and Soft-Point bullets. Hollowpoint bullets are currently the most popular choice for police and self-defense ammunition. Such bullets are designed with the hollow cavity in the nose (therefore the common name “hollowpoint”). This cavity causes the bullet to expand once it hits the soft tissue of human or animal body; thus results in reduced penetration but a wider wound channel. Softpoint bullets do not have the cavity in the nose but the lead core is exposed at the tip so bullet can easily deform in the target to provide larger wound channel.

JHP - Jacketed HollowPoint bullet

SJHP - Semi-Jacketed HollowPoint bullet

SP - Soft-Point bullet

Armor-piercing pistol ammunition is nowadays mainly intended for use against adversaries with body armor. The simplest AP bullets for handgun ammunition are usually made from solid brass or bronze; sometimes these bullets are made with pointed tips to further improve penetration. Since such bullets, because of their hardness, may cause excessive wear to the barrel, they may be covered with some a softer materiel, such as Teflon. In some cases, AP bullets are made with the traditional soft brass or other gilding-metal jacket and with a composite core, made of a hardened steel penetrator together with some other filler. One example of such ammunition is the Belgian FN 5.7mm SS190 bullet, which has core made partly of steel (front) and partly of aluminum (rear). Another example is the Russian 9mm 7N21 bullet, which has a hardened steel core that passes throughout entire bullet and is exposed at the tip; the space between the jacket and core is filled with polyethylene.

7.62x38R Nagant

Developed during 1890s, this cartridge was especially designed for Belgian Nagant revolvers which featured unique gas-seal action. The bullet is seated deep into the cartridge case, and prior to firing the cylinder of the revolver moves forward, so the cartridge mouth enters the barrel to provide gas seal between the cylinder and bore. It was extensively used in Russia and USSR, as well as in Poland. Today this round is obsolete.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

FMJ

7

270

255

flat-nose bullet deeply seated into the case

.38 Smith & Wesson (.38 SW)

Developed by famous company Smith & Wesson, this revolver cartridge was introduced in 1877 and over the following decades it was widely popular for compact revolvers. During WW2, a 'ball' (FMJ) version of this round was issued to British troops as .380/200 revolver cartridge. A slightly different version of the same round was also known as the .38 Colt New Police. Today this round is mostly obsolete.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

LRN

Remington

9.4

208

205

.38 Smith & Wesson Special (.38 SW Special)

This cartridge was introduced in 1902 as a stretched, more powerful version of the older .38 SW cartridge. It quickly became very popular in USA, and during better part of the 20th century it was the most widely used revolver cartridge there, for both civilian and police applications. It was also issued to certain military personnel, most notably to USAF and USN pilots during 1950s and 1960s.It is still quite popular and is currently produced by many ammunition manufacturers worldwide in a large number of versions, with loadings especially intended for target shooting, practice or self-defense. It must be noted that modern 'high pressure' rounds, usually marked with +P suffix, are NOT suitable for older revolvers, designed for standard pressure loadings.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

JHP

Remington

7.12

290

299

modern loading

JHP +P High Velocity

Federal

8.36

290

346

modern high pressure loading with Hydra Shok bullet

LSWC +P

Remington

10.2

270

374

modern high pressure loading

.357 Magnum

This round was created in around 1935 as a joint effort between Smith & Wesson and Remington to produce more powerful revolver round for American law enforcement. It caught up from the start and is still extremely popular for most practical purposes - sport shooting, self-defense, hunting. Over the time, quite a few carbines (mostly lever-action type) were also chambered for this round, and few semi-automatic pistols were built to fire it. Today .357 Magnum is produced by many ammunition manufacturers worldwide and in great many loadings.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

Golden Saber JHP

Remington

8.1

372

560

Express JHP

Remington

8.1

442

792

Hydra-Shok JHP

Federal

10.23

378

727

Express SP

Remington

10.23

376

723

Express JHP

Remington

11.66

350

714

Muzzle velocity shown from long (8") barrel

.41 Magnum

The .41 Magnum was created in 1964 to fill the gap between .357 Magnum and .44 Magnum rounds. This round failed to achieve high popularity of its older magnum-class 'neighbors' but still has a strong, although small, following among revolver shooters. It is still produced by several major ammunition manufacturing companies.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

Silvertip JHP

Winchester

11.34

380

825

Express JHP

Remington

13.6

396

1070

.44 Smith & Wesson Special (.44 Special)

This round was created by Smith & Wesson in 1907 as a stretched-out and more powerful version of the older .44 Russian round. Originally a black-powder number, it was soon converted to smokeless powder and is still produced in this form. This round is still popular for target shooting and self-defense.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

Silvertip JHP

Winchester

12.96

274

490

LRN

Winchester

15.55

229

408

Express LRN

Remington

15.94

230

421

.44 Magnum

When first introduced in 1956 as a joint effort between Smith & Wesson and Remington, this revolver round was advertised as a most powerful handgun cartridge in the world. While it is no longer holds this title, being outperformed by a number of monstrous loads of larger caliber, it is still a formidable number, suitable for a number of applications including long-range target shooting, self-defense (especially against dangerous animals) and hunting. Several semi-automatic pistols and carbines (lever-action and semi-automatic) were produced over the years to fire this cartridge. Today it is still manufactured by a number of makers worldwide.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

Express JHP

Remington

11.66

490

1409

Hydra-Shok JHP

Federal

15.55

360

1006

Core-Lockt JHP

Remington

17.82

376

1266

.45 Colt (.45 Long Colt, .45 LC)

This is one of the oldest revolver cartridges still in production today. It was introduced in 1873 along with famous Colt Single Action Army revolver, and was adopted by US military. Originally a strictly blackpowder loading, today this round can be found in both blackpowder versions (for old revolvers) and in smokeless loadings for modern revolvers and carbines.The alternate (and unofficial) designation .45 Long Colt (or .45LC in short) comes from relatively recent times, to distinguish it from another .45caliber military revolver loading of the 1875 era, the .45 Shofield, which featured shorter case and lighter charge.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

LRN

16.2

274

610

original black powder load of 1873

Silvertip JHP

Winchester

14.58

280

575

modern smokeless load

Express LRN

Remington

16.2

262

558

modern smokeless load

.455 Webley

The .455 Webley Mk.I ammunition was adopted by British army in 1887. With introduction of the cordite propellant this round was changed to .455 Mk.II with slightly longer case, which was also used for latter versions (Mk.III to Mk.V), which featured different bullets. All .455 revolver ammunition was officially declared obsolete by British military in around 1950. Some manufacturers still produce this ammunition for older guns, although no new guns were made for these loadings for quite some time.

Designation

Manufacturer

Bullet weight, g

Muzzle velocity, m/s

Muzzle energy, J

Comments

.455 Mk.I

17.7

213

390

original black powder load

.455 Mk.II

17.2

177

268

original cordite loading of WW1 era

.455 Mk.II

Fiocci

16.9

259

566

modern commercial loading

.500 Smith & Wesson Magnum

The .500 SW Magnum is most recent and most monstrous revolver magnum-class round. It is chambered in specially designed S&W X-frame revolvers and several carbines. The most obvious purposes for this round are hunting and protection from large and dangerous animals such as grizzly bears.